/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.replication;

import java.io.IOException;
import java.util.List;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.hadoop.hbase.ServerName;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Base implementation class for replication tracker.
 */
@InterfaceAudience.Private
abstract class ReplicationTrackerBase implements ReplicationTracker {

  private static final Logger LOG = LoggerFactory.getLogger(ReplicationTrackerBase.class);

  // listeners to be notified
  private final List<ReplicationListener> listeners = new CopyOnWriteArrayList<>();

  private final AtomicBoolean initialized = new AtomicBoolean(false);

  @Override
  public void registerListener(ReplicationListener listener) {
    listeners.add(listener);
  }

  @Override
  public void removeListener(ReplicationListener listener) {
    listeners.remove(listener);
  }

  protected final void notifyListeners(ServerName regionServer) {
    LOG.info("{} is dead, triggering replicatorRemoved event", regionServer);
    for (ReplicationListener listener : listeners) {
      listener.regionServerRemoved(regionServer);
    }
  }

  @Override
  public final Set<ServerName> loadLiveRegionServersAndInitializeListeners() throws IOException {
    if (!initialized.compareAndSet(false, true)) {
      throw new IllegalStateException(
        "loadLiveRegionServersAndInitializeListeners can only be called once");
    }
    return internalLoadLiveRegionServersAndInitializeListeners();
  }

  protected abstract Set<ServerName> internalLoadLiveRegionServersAndInitializeListeners()
    throws IOException;

}
